Israeli Prime Minister Benjamin Netanyahu has claimed that Hezbollah-the Lebanon-based, Iranian-backed, politico-military terrorist organization-was responsible for the suicide bombing in Bulgaria that killed five Israeli tourists. Amid ongoing U.S. and Israeli threats to strike Iran's nuclear facilities, the bombing raises a critical concern about any potential conflict: a very capable Hezbollah, together with Iran, would likely strike back hard and not only in the Middle East, drawing the United States into another prolonged and bloody conflict in the Muslim world that it doesn't need. Such a scenario should make those advocating war with Iran take pause.

War-weary Lebanese do not want their country turning into another battleground against Israel. Hezbollah would also risk alienating its predominately Shiite political constituency. But the ideological and financial ties between top leaders in Tehran and Hezbollah could trump such considerations, especially in the event of an Israeli or Israeli-U.S. attack on fellow Muslims in Iran.

Iranian leaders-in danger of losing a vital ally in Syria-may not risk another surrogate's fall in a confrontation with Israel. But that is far from a sure thing. Current and former U.S. officials recently told the Washington Post that should Israel strike Iran, Hezbollah's global network would launch more terrorist attacks. A multi-front conflict could ensue that would rope in America. If Israel starts a war with Iran it is unable to finish, Israel could leave the heavy lifting to the United States while it defends its own borders against Hezbollah.

As President Barack Obama proclaimed earlier this year, "We've got Israel's back." On the one hand, America's historic-and expanding-cooperation with the Jewish state signifies an enduring commitment to Israel's security. On the other hand, the unpredictable nature of any potential conflict speaks to the importance of U.S. diplomacy with Hezbollah's patron, Iran.

Iran's Revolutionary Guards have been training Hezbollah since it emerged in the early 1980s. The group eventually came into its own, launching sophisticated guerilla attacks against Israeli military units. Today, the U.S. Department of Defense estimates that Hezbollah receives $100 to $200 million annually from Tehran, as well as training, weapons, and other assistance.

Based on the historical record, it is unlikely that Hezbollah would remain on the sidelines. In 1996's Operation Grapes of Wrath, the group contested Israel's massive air and ground firepower with hundreds of rocket attacks into Israel proper. In the summer of 2006, following Hezbollah's abduction of two Israeli soldiers, Israeli Defense Forces (IDF) launched air and ground attacks over Lebanon, and Hezbollah used real-time signals intelligence to ambush Israeli commandos, and fired more than 4,000 rockets into northern Israel, one of the most serious assaults on the Jewish state. Neither Israel nor Hezbollah scored a decisive victory. A stalemate between the Levant's American and Iranian clients could play out again.

As Hezbollah has evolved from guerilla incursions to conventional campaigns, the group has exposed Israel's conventional weaknesses, but also provided Israel an opportunity to correct its mistakes. Hezbollah could face massive Israeli ground and air assaults. Nevertheless, leaders in Washington and Tel Aviv also have a troubling history of underestimating their adversaries. Regional expert Nicholas Noe describes Hezbollah as "one of the more successful actors the U.S. has dealt with in hiding capabilities."

Indeed, rigorous accounting of Hezbollah's current military tactics and capabilities is lacking. Last year, Hezbollah successfully unraveled the CIA's spy network in Lebanon, identifying and capturing American spies who had infiltrated Hezbollah's ranks. Little is known about the group since the 2006 war. U.S. ambassador to the United Nations, Susan Rice, has accused Syria of colluding with Iran to arm Hezbollah with more potent weapons. The IDF's assessment is that Hezbollah possesses long-range, surface-to-air missiles and Russian-made air-defense systems. Additionally, it is estimated that the group has a firebase of over 10,000 fighters and between 60-80,000 missiles and rockets.

Hezbollah would certainly face torrential Israeli ground and air offensives. But the possibility that any conflict could result in a pyrrhic deadlock is worrying, not only for Israel but also for America.

Over the past year, American leaders have ratcheted up tensions with Tehran while doing little to reassure Israelis reluctant to rely on America. Beating the drums of war could spell doom as a form of psychological pressure. If Israel attacks Iran and Hezbollah missiles rain down on Israeli streets, America may be pulled into conflict with a capable and resilient guerilla foe that it knows very little about.

Malou Innocent is a foreign policy analyst at the Cato Institute. Dr. Ehud Eilam formerly served in the Israeli Ministry of Defense, and specializes on the Middle East and Israeli military doctrine.